This invention relates to an apparatus and method for cutting a gold ribbon to a predetermined length and then placing a piece of cut ribbon (the preform) on an integrated circuit (IC) die base in preparation for IC die placement and attachment.
The gold ribbon used in the process of the present invention is often less than 2.0 mils in thickness and must be cut to length within a tolerance of, for example, 0.0005 inches, and then precisely placed on the IC die base. Precision is required so that during bonding with a die-attach machine, the preform contacts and is properly bonded to the die that is placed on top of the preform. Preforms that are too short will result in poor bonding or voids. Preforms cut too long will not seat properly in the die base.
A preform is typically 0.200 to 0.400 inches in length, with a thickness of 0.002 inches and width of 0.150 to 0.400 inches. It must be precisely placed on the ceramic base in the XY plane (horizontal) and Z direction (vertical).
The prior art hitch feed preform dispenser widely used in the industry illustrated in FIG. 1 is by Kulicke. It is controlled by a cam assembly driven by a motor. The numerous rollers and linkages are subject to wear which induces inaccuracies in cutting the gold ribbon to precise length and in positioning the preform on the IC die. The operation of this device is set forth in detail below.
Additionally, U.S. Pat. No. 3,149,510 issued on Sept. 22, 1964, discloses a fine wire manipulator and bonding instrument for transistors. The device does not cut the wire but merely positions the wire correctly for bonding when manually activated.
Finally, U.S. Pat. No. 4,422,568 issued on Dec. 27, 1983, discloses a method of making constant bonding wire tail lengths as part of a high speed automatic fine wire bonding machine.